High-complexity integrated circuits, such as a microprocessor integrated in a single chip, for example, are known to include a plurality of sub-circuits, commonly termed modules, which are interfaced by suitable electrical connections carrying system signals. These signals may either be data or control signals which are transmitted under management by a supervisory module, such as a CPU.
Each of the modules included in a single integrated circuit is intended to implement a specific function. For example, certain modules may function as analog-to-digital converters, or serial circuits, or logic units, etc. An individual module contains an interface circuit enabling it to communicate with other modules.
FIG. 1 shows schematically a portion of a final integrated circuit CIF comprising four modules and being assembled in a conventional manner. In this example, the final integrated circuit CIF portion comprises first 1, second 2, third 3 and fourth 4 modules, respectively designated LOGICA.sub.-- 1, LOGICA.sub.-- 2, LOGICA.sub.-- 3 and LOGICA.sub.-- 4. These four modules have first IF1, second IF2, third IF3 and fourth IF4 interface circuits, respectively, which are respectively designated INTERFACCIA.sub.-- 1, INTERFACCIA.sub.-- 2, INTERFACCIA.sub.-- 3 and INTERFACCIA.sub.-- 4.
It should be noted that the modules in an integrated circuit may come in two general categories: simple modules, which are characterized by having a small number of transistors and a simple interface circuit (the modules 2, 3 and 4 in the example of FIG. 1); and complex modules, which are characterized by having a large number of transistors and either a simple or complex interface circuit (such as module 1 in the example of FIG. 1).
When formed on a semiconductor, the layout of each of these modules, whether simple or complex, is usually given an aspect ratio, or length-to-width layout ratio, aimed at producing the densest possible integrated circuit. The different modules are then assembled, either manually or automatically, into the final integrated circuit CIF portion.
The schematic presentation of FIG. 1 brings to light some limitations of this conventional assembly method, as specified below.
1. A high silicon area requirement, for interfacing the individual modules. The final integrated circuit CIF portion of FIG. 1 includes a number of interface circuits equal to the number of modules, and a complicated pattern of buses 5 must be provided for supplying these interface circuits IF1, IF2, IF3 and IF4.
2. An intensification of the capacitance driven from a common system bus 8, connected to the complicated pattern of buses 5 and to additional connection buses 6 and 7, resulting in the speed of the final integrated circuit CIF portion being slowed.
3. More complicated assembling of the individual modules 1, 2, 3 and 4, resulting in lengthened times for developing the final integrated circuit CIF.
An alternative approach would be to make all modules, both simple and complex, with the same length, so as to simplify the assembling procedure. However, even this alternative approach has a serious drawback. In fact, the modules it produces would not be individually optimized, while a large area would be occupied by internal connections commonly known as the connection paths.